1. Field of the Invention
This invention relates to a new and improved ultrasonic method and apparatus for noninvasive biophysical diagnosis.
2. Prior Art
Prior art acoustical interrogation methods and apparatus are described in Beretsky et al, U.S. Pat. No. 3,830,223, issued Aug. 20, 1974 entitled "Methodology and Apparatus for Non-Invasive Bio-physical Diagnosis"; Beretsky et al, U.S. Pat. No. 3,934,458 issued Jan. 27, 1976, and entitled "Method and Apparatus for Pulse Echo Imaging and Characterization of Bodies"; and Beretsky et al U.S. Pat. No. 4,063,549 issued Dec. 20, 1977, entitled "Ultrasonic Method and Apparatus for Imaging and Characterization of Bodies", wherein the technique of coherent detection, i.e., detection and processing of both amplitude and phase in reflected acoustical energy pulses, is generally described.
One technique of the prior art utilizes time domain and frequency domain signal processing techniques which are cumbersome and require enormous computer capacity (i.e., '223 and '549). Because of the nature of the acoustical pulses used in ultrasonic interrogation, mathematical singularities arise which are difficult to overcome and lead to appreciable degradation of the information. In the signal processing techniques utilized by the prior art, each echo returned is processed by first storing the individual return in a suitable memory, and is then followed by the use of signal processing algorithms which require significant processing time. The need for large amounts of memory and processing time to detect a returned echo, severely limits the application of these techniques to only those ultrasonic examinations which can be rapidly detected.
Another technique of the prior art (i.e., '458) detects polarity and amplitude of the returned echo without the need for complex signal processing by utilizing a specific acoustic pulse wave shape. However, achieving the desired wave shape is a difficult task and is complicated by minor imperfections in the manufacture of practical transducers. Both difficulties substantially reduce the effectiveness of this technique. Commonly utilized transducers produce more complex acoustic pulses than can be adapted to this process.